1. Field of the Invention
This invention pertains to a medical apparatus for passage into a body lumen of a patient. More particularly, this invention pertains to an emboli filter for deployment in a patient's body lumen to capture emboli entrained in fluid flowing through the lumen.
2. Description of the Prior Art
There are numerous medical procedures for introducing tools into a patient's body lumen. For example, occlusion treatment tools (such as angioplasty balloon-tipped catheters, stents or ablation catheters) may be admitted into a lumen of an artery to treat an occluded site within the artery. A balloon tipped catheter may be expanded at the site to urge the occlusion against the walls of the artery to improve patency of the arterial lumen. A stent may be expanded at the site to maintain lumen patency. Alternatively, or in combination with other procedures, an ablation tool may be used to mechanical remove the occluding material.
The manipulation and use of tools within a lumen of a body passage may cause the release of emboli in the lumen. In arteries, such emboli become entrained within blood flow within the artery. Such emboli can contribute to morbidity. For example, emboli can be transported to the brain and contribute to cranial ischemia (stroke). In treating occlusions in coronary arteries, emboli may flow to occlude distal, micro-vessels contributing to myocardial ischemia.
In order to reduce morbidity associated with emboli, filters have been developed to capture emboli for removal from the lumen. An example of such a filter is shown in U.S. Pat. No. 5,695,519. Typically, such filters include a filter media carried on an elongated, flexible member. The filter media commonly has an open cell construction with a cell or mesh size of 50–300 micrometers (μm) to capture emboli while permitting fluid (e.g., blood) flow past the filter. The filter media is opened and closed in an umbrella-like fashion. In the open position, the filter media substantially fills the cross-section of the body lumen such that substantially all emboli-laden fluid flow must pass through the filter media. When closed, the filter media captures the emboli and the filter is reduced in size to pass through the lumen for removal.
Emboli filters should be easy to use and highly flexible to pass through narrow vasculature. The filters should open in a manner atraumatic to the vessel. The filter should open in a manner to accommodate a non-circular cross-section while covering as much as possible of the cross-sectional area of the vessel. Such a filter need not abut the wall of the vessel since fluid flow at the wall is turbulent and emboli-laden flow is spaced from the wall. Preferably the filter media is highly flexible and the filter design permits a long filter to enlarge filter volume.